As a technology of improving both usability and a sense of luxury by automatically opening a lid of a vanity case and controlling its opening speed, there is known a prior art disclosed in Japanese Patent Application Laid-open No. 2006-36263. In this prior art, a shaft (pin) disposed in a case body is inserted into a shaft holding portion provided at the lid, an urging means is provided for urging the lid in an opening direction, and viscous material is charged between the shaft and the shaft holding portion such that the lid is slowly opened with respect to the case body. In the above-mentioned case, the shaft holding portion provided at the lid can be rotated around the shaft in accordance with the opening operation of the lid, and at that time, the viscous material resists against the relative rotation between the shaft and the shaft holding portion, so that the speed of rotation of the lid due to the urging means is controlled.